Question: Which of these numbers is composite? ${2,\ 7,\ 13,\ 31,\ 93}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 2, 7, 13, and 31 each have only two factors. The factors of 93 are 1, 3, 31, and 93. Thus, 93 is the composite number.